This invention relates to an apparatus and a method for filling trays with rod-shaped smokers' articles.
The smokers' articles that can be handled by the apparatus of this invention are, in particular, cigarettes or filters, but without this invention being considered as applicable to the handling only of these articles. For simplicity, in this description, reference is made to the handling of cigarettes and to the filling of cigarettes into containers commonly known as “trays”, which are widely used in the tobacco processing industry to feed rod-shaped smokers' articles to operating machines such as cigarette packers, machines for applying filters to cigarettes or machines for making filters.
Known in the prior art are numerous apparatuses for filling trays with smokers' articles where cigarettes are conveyed in bulk from the cigarette machine to the tray filling apparatus on a horizontal conveyor belt and the cigarettes are filled into the trays by allowing the cigarettes to drop vertically into a tray below which is replaced by an empty tray when it is full.
The horizontal conveyor belt terminates at the top of a customary cigarette hopper equipped internally with agitator elements. Under the hopper there is a device, usually called “rack”, consisting of two rows or combs of rotary bars having circular or square cross section, which opposes the cigarettes and allows them to drop into the underlying tray in a manner uniformly distributed across the full width of the tray itself. The rotation of the bars facilitates controlling the downward flow of the mass of cigarettes above the bars.
When just loaded, a new tray is at a raised position and therefore the rack is near the bottom of the tray. As it fills, the tray moves down continuously in such a way that the distance between the rack and the top of the mass of cigarettes inside the tray, that is to say, the drop distance of the cigarettes, remains limited and substantially constant.
At the top of the hopper there is a variable capacity buffer zone to compensate for the down time due to changing of trays and equipped with optical sensors for detecting the filling level and if necessary stopping the cigarette making machine if the maximum level is reached.
Prior art tray filling apparatuses of more recent type, in certain operating situations, allow the mass of cigarettes from the cigarette maker to flow continuously towards the infeed of a cigarette packer located downstream of the tray filling apparatuses. In such a situation, the rack remains closed and the hopper is full of cigarettes.
When the tray has to be changed, the full tray is made to withdraw on suitable rails under it and an empty one is lowered into its place just under the rack. In the meantime, the rack is closed to prevent cigarettes from dropping out.
Apparatuses of the type described above have some disadvantages.
When the rack is closed, some of the cigarettes may be “pinched”, resulting in cigarettes being damaged and incorrectly positioned. These cigarettes do not move down into the underlying tray and may knock the cigarettes under them out of place or cause them to fall out onto the floor.
Furthermore, vibration and shaking as the cigarettes pass through the rack causes some of the tobacco to fall out of the cigarette ends and after passing through the rack, the cigarettes fall freely and the tray is not filled entirely uniformly even if the tray does move down slowly under the rack as filling progresses.
In the operating situation described previously where the mass of cigarettes from the cigarette maker flows continuously towards the infeed of a cigarette packing machine downstream, large numbers of cigarettes forming part of the cigarette flow in transit above the hopper roll over the cigarettes at the top of the hopper causing them to deteriorate.
Moreover, in prior art tray filling apparatuses it is not possible to exceed a certain maximum tray filling speed, which means these apparatuses cannot be associated with cigarette makers capable of producing more than 16,000 cigarettes per minute.